1. Field of the Invention
The present invention relates to buckles and more particularly, to a safety buckle that can be automatically unlocked when received a stretching force within a predetermined range of angles.
2. Description of the Related Art
U.S. Pat. No. 7,069,625 discloses a safety buckle 60. According to this design, the safety buckle 60 comprises a first female buckle member 80a, a second female buckle member 80b, and a male buckle member 70. The male buckle member 70 has two plug units 71a and 71b respectively inserted into the receiving open chamber 81a of a first female buckle member 80a and the receiving open chamber 81b of a second female buckle member 80b. Each plug unit 71a and 71b has two raised engagement portions 72a and 72b respectively protruded from the top and bottom sides for engaging respective recessed engagement portions 82a and 82b of the respective female buckle members 80a and 80b respectively.
The aforesaid safety buckle 60 is for use in a collar for cat. The collar can automatically be unfastened if the collar is detained by an object during jumping of the cat, preventing a hurt to the cat. In other words, the safety buckle is automatically unlocked to unfasten the collar from the cat for letting the cat go freely without hurt when the collar received a stretching force over the limited range (normally about 10 lbs or 5 kgs). A collar for cat is normally used for holding a nameplate, bell, or any of a variety of ornamental devices.
Because the female buckle members 80a and 80b of the aforesaid safety buckle 60 are not rotatable relative to the male buckle member 70, the safety buckle 60 can be easily unlocked only when the collar receives a stretching force in parallel to the direction of the central axis 75 extending through the safety buckle 60, i.e., the safety buckle 60 can be unlocked only when stretched in a particular angle. Therefore, the safety level of this design of safety buckle is not high.